"Do It Again" is a song by American rock band The Beach Boys, written by Brian Wilson and Mike Love, who also share lead vocals. Produced by Wilson as a self-conscious callback to the band's earlier surf-based material, the song was released as a single on July 8, 1968, and subsequently placed on the band's 1969 album, 20/20. The single's B-side, "Wake the World", is taken from Friends, released the month before.

"Do It Again" is a self-conscious callback to the band's earlier surf-based material. The lyrics to the song, originally entitled "Rendezvous", were inspired after a day Mike Love had spent at the beach in which he had gone surfing with an old friend named Bill Jackson. Mike then showed the lyrics to his cousin Brian Wilson, who proceeded to write the music to Mike's lyrics of nostalgia. Brian has stated in the past that he believes the song was the best collaboration that he and Mike ever worked on. In 2013, Love noted, "I came back from a surfing trip with some high school buddies and said: 'Hey Brian, I just went to the beach and the waves and the girls were great. We've got to do a song called "Do It Again".' He remembers it being at my house. I remember it as being at his house. He starts pounding at the piano, I was summoning up the words and we got a chorus together, which was basically a bunch of doo-wop inspired harmonies. We created that whole song in fifteen minutes."

Many critics and fans noted the return to the surfing style, which the band had generally avoided since 1964. Carl later explained the transition back to their old style in Melody Maker:

"Yes, I suppose it has got the old Beach Boys surfing sound. It's back to that surfing idea with the voice harmony and the simple, direct melody and lyrics. We didn't plan the record as a return to the surf or anything. We just did it one day round a piano in the studio. Brian had the idea and played it over to us. We improved on that and recorded it very quickly, in about five minutes. It's certainly not an old track of ours; in fact it was recorded only a few weeks before it was released. We liked how it turned out and decided to release it."

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